Weight Loss Drugs: What You Should Know

If you've struggled to lose weight through diet and exercise alone, you may wonder if prescription weight loss medications could help. Weight loss drugs may be an option if you have obesity, which is a body mass index (BMI) of 30 or higher. Your doctor may also prescribe the drugs if your BMI is at least 27 and you have one or more weight-related health conditions, such as diabetes or high blood pressure.

The newest prescription drugs approved to treat obesity are semaglutide (Wegovy) and tirzepatide (Zepbound). Other older medications include liraglutide (Saxenda), naltrexone-bupropion (Contrave), orlistat (Alli, Xenical), and phentermine-topiramate (Qsymia).

Glucagon-like peptide-1 (GLP-1) agonists are used to treat both obesity and type 2 diabetes. GLP-1 is a hormone that's found in your digestive system. It's released when you eat and tells your body to make insulin to control your blood sugar. It also slows down how quickly your food moves from your stomach to your intestines and gives your brain the signal that it feels full. Here are some examples of GLP-1 drugs:

Wegovy is a shot you give yourself once a week with a prefilled pen in the skin of your abdomen, thigh, or upper arm. You start with a low dose and increase it gradually over several months. In the largest clinical trial that tested Wegovy before its FDA approval, people taking the highest dose lost, on average, more than 12% of their body weight over 17 months.

Ozempic is the same medication as Wegovy. It isn't approved for weight management, although many people taking it do lose weight. It's sometimes prescribed off-label for that purpose.

Liraglutide is one of the older GLP-1 drugs. It's a daily shot that increases in dose over time. If you don't lose 4% of your weight after 16 weeks of taking liraglutide, your doctor may tell you to stop taking it because it's unlikely to work for you.

You take tirzepatide as a weekly injection. It isn't approved for treating obesity, but during tirzepatide diabetes trials, researchers noted people who got tirzepatide lost much more weight than those on standard diabetes therapy.

Side effects of GLP-1s include nausea and vomiting, which usually improves over time, diarrhea or constipation, headache, fatigue, and abdominal pain. It's important to note that these medications are intended for long-term use. Weight loss typically plateaus after about a year, and some weight regain may occur if the medication is stopped. The long-term effects of GLP-1s are still being studied.

While GLP-1s have taken center stage, several other medications are approved for weight loss:

Taken as a daily pill, this is a combination of an appetite suppressant and an anticonvulsant. Phentermine reduces your appetite, while topiramate increases feelings of fullness. Possible side effect include tingling in hands and feet, dizziness, insomnia, constipation, and dry mouth.

This daily pill is a combination of an opioid antagonist and an antidepressant. Naltrexone helps control food cravings, while bupropion helps reduce your appetite. Possible side effects include nausea, constipation, headache, vomiting, and dizziness.

This is a pill that's taken three times a day with meals that contain fat. It works by blocking the absorption of about 30% of fat from food. Possible side effects include oily stools, gas and oily spotting, frequent bowel movements, and abdominal pain.

Phentermine is an appetite suppressant pill that you can use short-term (up to 12 weeks). It decreases your appetite by affecting the central nervous system. Side effects include increased heart rate and blood pressure, insomnia, nervousness, and constipation.

Your doctor will help you select a weight loss drug based on your weight and overall health, other medications you are taking, whether you plan to become pregnant, potential side effects, and cost and insurance coverage. Weight loss drugs can be expensive and not all are covered by insurance.

Most people see the most significant weight loss in the first six months of treatment. Weight loss often slows down or plateaus after six to 12 months. If medication is stopped, some weight regain is common. These drugs work best when combined with a healthy diet and regular exercise. Your doctor will monitor your progress and any potential side effects. Your medication or dosage may be adjusted based on how your weight loss is going and any side effects you're having.